Giant, wooden balls in the Paris sewer museum home page site map
Title: Giant, wooden balls in the Paris sewer museum
Description: Balls like these have been used for centuries to clean the Paris sewer system. Each ball's diameter is slightly less than the diameter of the passage it is used to clean. When a ball is placed in a sewer passage, the sewage is forced to pass the ball through the small opening that remains between the ball and the walls of the passage. This pressurizes the sewage and makes it move quickly, helping to flush solid matter. Yuck.



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